Simultaneously preparing a plurality of delivery rounds or “sequencing” in a sorting machine is a well known process. Simultaneously preparing a plurality of delivery rounds on the same sorting machine raises the problem of separating the delivery rounds.
In order to separate two delivery rounds, it is known that mail items inserted into the machine can be sorted in a first sorting pass by using “virtual” delivery points (delivery points that do not exist and that are assigned to respective sorting outlets of the machine). That technique suffers from the drawback of limiting the sorting capacity of the machine as regards the number of delivery points that can be handled in a second pass for preparing delivery rounds.
In another known method of handling mail items for preparing delivery rounds, the mail items of two different delivery rounds are separated by shifting sorting outlets in the second sorting pass, i.e. the delivery points of one delivery round are assigned sorting outlets that are different from the sorting outlets assigned to the delivery points of another delivery round. That technique also suffers from the drawback of limiting the sorting capacity of the machine as regards the number of delivery points that can be handled in the second pass for preparing delivery rounds.
In another known method of handling mail items for preparing delivery rounds, colored separator boards are used to separate the items of different rounds physically. With that method, the delivery points of the delivery rounds are concatenated in the sorting outlets of the machine, i.e. they are put one after another in the sorting outlets (the last delivery point of one delivery round being followed directly by the first delivery point of the following delivery round in the same sorting outlet) and two adjacent mail items in the same sorting outlet that correspond to different delivery rounds are separated by a separator board. With that technique, if N1 is the number of sorting outlets of the machine that are used in the first pass, and N2 is the number of sorting outlets of the machine that are used in the second pass, it is possible to sort N1×N2 delivery points in the second pass. The use of separator boards gives rise to additional costs through loss of throughput (additional object to be handled, manipulations by the operator, etc.). Nevertheless, that solution is in use for objects stood on edge but it is unsuitable for objects laid flat (impossible to locate a separator).